Flexible containers for the storage of blood or other medical fluids composed from blow-molded polyolefin polymers are generally well known. One current formulation for blood containers is disclosed in Gajewski et al., U.S. Pat. No. 4,140,162, assigned to the present assignee. It is desirable to attach to such blood containers flexible donor tubing and flexible port tubes composed basically of polyvinyl chloride (PVC). Such tubing, however, is sealingly incompatible with the polyolefin polymer of the bag itself. Therefore, some intermediate method or connector is necessary to effectively join the tubing to the blood container.
One method and an adaptor for accomplishing this is shown in Kwong et al., Ser. No. 067,068, a pending application assigned to the present assignee. Kwong uses a particularly designed adaptor, composed of a single material, as an intermediate link between the container and the tubing. The tubing and the container are respectively mechanically sealed to the adaptor and the connection between the two thus effected. The present invention seeks another method for sealing the dissimilar materials using a different type of connecting element.
The solution of the present invention is basically to utilize a small connector or bushing comprising two separate and distinct layers of different polymers, one coextruded or co-injection molded over the other. In the preferred embodiment, the inner layer is composed of polyvinyl chloride while the outer layer is composed of a lower melting polymer capable of being compatibly sealed or melted to the polyolefin container, such as poly(ethyl-vinyl acetate) (EVA).
To effect the connection, the polyvinyl chloride tubing or port tube is first sealed within the two-layered connector, with the PVC layer of the connector bonded to the PVC tubing, by any conventional means such as solvent sealing with cyclohexanone. The tubing or tube with connector attached is then cleaned and prepared for insertion in the polyolefin blood container. The connector is placed within the blow-molded opening in the polyolefin container and held in place by a frictional fit. The container with connector and tubing attached is then heated to a temperature sufficient to cause the EVA layer of the connector to melt and fuse with the polyolefin container, forming a solid secure seal.
One convenient method of effecting this heating is to place the unit prior to sealing into a conventional sterilization apparatus and autoclaving it to sterilization temperature. This operation combines two functions; namely, sterilizing the entire system prior to use, and heating the connection to a temperature sufficient to cause the EVA layer of the connector and the polyolefin container to fuse together.
An alternative method of heating the EVA layer is to use a radio frequency sealing technique, bombarding the EVA-polyolefin connection with sufficient radio waves to cause the EVA to melt, and the pieces to fuse together.
The connector may be formed from conventional formulations of plasticized polyvinyl chloride and EVA using standard plastic coextrusion equipment. The two plastic formulations are appropriately charged into a conventional screw coextrusion system, and extruded at a temperature of about 300.degree. to 350.degree. F. The layered plastics come from the extruder as a length of tubing which, upon cooling, is cut into connectors or bushings of appropriate length. The multi-layered tubing for making the connectors may also be co-injection molded using standard co-injection molding equipment.
Preferably, the EVA outer layer of the connector is substantially thinner than the polyvinyl chloride inner layer since not as much EVA is needed to effect the heat seal and shrinking or other undesirable deformation of the EVA layer is minimized.
In a variation of the present invention, the port itself may be coextruded from EVA and PVC, as the connector above, and the port sealed within the polyolefin container as disclosed in the present invention. A conventional PVC port protector may then be sealed around the tube port.
In the handling of a medical product, container, or apparatus it is frequently desirable to exclude possibly contaminating solvents or other agents from the fabrication process. In a second embodiment of the present invention, the same coextrusion technology may be used to effect a solventless seal between containers of similar materials, such as polyvinyl chloride.
Two coextruded connectors, similar to that described above, are utilized. The sequence of polymer layers of each, however, is reversed, one from the other. In this case, one connector has an outer layer composed of PVC and an inner layer of EVA. A second connector or bushing, appropriately sized to fit snugly within the first connector, is extruded with the layers reversed; that is, the outer layer is EVA and the inner layer PVC.
The respective PVC layers of each connector are sealed to the corresponding PVC items which are to be joined. This sealing may be accomplished by conventional solvent sealing means, radio frequency sealing or other method.
For final assembly, the connectors are frictionally fit one within the other, EVA layer to EVA layer. The united connectors are then heated by conventional heat-sealing means, by radio frequency sealing, or other means, to a sufficient temperature to cause the EVA layers to melt and fuse together forming a solid bond.
This method for sealing like materials together using multi-layered connectors has the additional advantage, in addition to solventless sealing at time of final assembly, of accomplishing the heat-sealing at a lower temperature than necessary to seal PVC to PVC. This avoids or prevents any potential decomposition or deformation of the PVC at temperatures sufficient to fuse them directly.